> For the complete documentation index, see [llms.txt](https://docs.pepay.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.pepay.io/architecture/technologies-and-architecture-of-pepay.md).

# Technologies & Architecture of PePay 🚀

Technologies Used in PePay 🌐

PePay leverages a modern stack to ensure security, scalability, and performance for seamless cryptocurrency payment processing. Here's an overview of the core technologies:

#### 1. **Backend Technologies** ⚙️

* **Node.js**: A lightweight, high-performance runtime for handling asynchronous operations and building scalable APIs.
* **Express.js**: Simplifies the creation of RESTful APIs to serve the backend.
* **PostgreSQL**: A robust relational database for storing user data, invoices, and transactions.
* **GraphQL (Optional)**: Enables flexible and efficient querying for complex use cases.
* **Webhooks**: Provides real-time updates to merchants for payment and invoice events.

#### 2. **Blockchain Integration** 🔗

* **Ethereum (EVM-compatible chains)**: Supports Ethereum, BSC, Avalanche, and Arbitrum.
* **Solana**: Offers fast and low-cost transactions.
* **Token Management**: Handles various tokens like ETH, SOL, and USDC.

#### 3. **Front-End & Dashboard** 🖥️

* **React.js**: Powers the merchant and admin dashboards for an intuitive user interface.
* **Tailwind CSS**: Provides responsive and visually appealing design.
* **Iframe Embed**: For seamless integration of payment interfaces.

#### 4. **Payment Features** 💰

* **Live Exchange Rates**: Uses APIs like CoinGecko to fetch real-time token-to-USD conversion rates.
* **Automatic Token Conversion**: Converts crypto to stablecoins (e.g., USDC) based on merchant preferences.
* **Secure Transactions**: Validates and confirms payments using blockchain data.

#### 5. **Security** 🔒

* **Encryption**: Protects sensitive data, including API keys and user information.
* **Rate Limiting**: Prevents abuse of APIs by limiting requests.
* **Webhook Authentication**: Ensures the authenticity of notifications sent to merchants.

***

### PePay’s Architecture Overview 🏗️

PePay is designed with a modular and scalable architecture to handle a wide variety of crypto payment scenarios. Here's a high-level view of its components:

#### **High-Level Architecture Diagram** 📊

```plaintext
             ┌───────────────┐
              │   Merchant    │
              │  (Front-End)  │
              └──────┬────────┘
                     │
                     ▼
        ┌─────────────────────────────┐
        │  Payment Backend (API)      │
        │  - Auth & API Keys          │
        │  - Invoice Management       │
        │  - Token & Chain Config     │
        │  - Webhook Dispatch         │
        └─────────────┬───────────────┘
                      │
           ┌──────────┴───────────┐
           │                      │
           ▼                      ▼
   ┌─────────────────┐    ┌───────────────────┐
   │    EVM Chain    │    │   Solana Chain    │
   │(Node or Indexer)│    │ (RPC or Indexer)  │
   └─────────────────┘    └───────────────────┘

           ┌───────────────────────────┐
           │ Database (invoices,      │
           │ users, tokens, etc.)     │
           └───────────────────────────┘
```

***

#### Key Components 🧩

**1. Backend (API Layer) 🌟**

* Exposes RESTful and/or GraphQL APIs for:
  * User authentication and management.
  * Invoice creation and retrieval.
  * Payment tracking and status updates.
* Manages token configurations, exchange rates, and user preferences.

**2. Blockchain Monitoring 🔗**

* Connects to blockchain nodes or indexers (e.g., Infura, QuickNode) for:
  * Detecting transactions in real-time.
  * Verifying payment amounts and token types.
* Uses WebSocket or polling methods for transaction monitoring.

**3. Database 🗄️**

* Central storage for:
  * Users, invoices, payments, and tokens.
  * Exchange rate history for accurate record-keeping.
* Optimized with JSON fields for flexibility in storing metadata.

**4. Merchant & Admin Portal 🖥️**

* User-friendly dashboards for:
  * Managing invoices and payments.
  * Setting token preferences.
  * Monitoring analytics and reports.

**5. Webhooks 🔔**

* Sends notifications to merchants about payment statuses:
  * Paid, expired, underpaid, or overpaid.
* Supports signature-based authentication for secure communication.

**6. Security Measures 🔒**

* Implements industry-standard practices:
  * HTTPS for API communication.
  * Encrypted storage of sensitive data.
  * Time-based API keys for enhanced security.

***

#### Benefits of PePay’s Architecture 🎯

1. **Scalability**: Modular design allows for easy addition of new blockchains or tokens.
2. **Flexibility**: Merchants can choose token preferences globally or per invoice.
3. **Security-First**: Advanced measures ensure data integrity and transaction safety.
4. **User-Centric**: Simple integration and customizable features for businesses.

This robust architecture ensures PePay remains reliable, secure, and easy to use for merchants globally. 🌍